Some radiation detectors for detecting radiation such as gamma rays look like that which is shown in FIG. 21. Such a radiation detector 51 has a scintillator 52 wherein scintillator crystals c are arranged three-dimensionally in the length, width, and height directions, and a photodetector 53 for detecting fluorescence emitted from the scintillator 52. The fluorescence that is emitted by the scintillator 52 is that which has been converted from radiation (see, for example, Japanese Unexamined Patent Application Publication 2004-279057).
The radiation detector 51 has a function for discriminating the part of the scintillator 52 that emitted the fluorescence when fluorescence is measured. Such a function is known as a fluorescence location discriminating function. The radiation detector 51 identifies the location of the fluorescence by identifying which of the scintillator crystals c that structure the scintillator 52 emitted the fluorescence.
If the scintillator 52 were structured by simply arranging the scintillator crystals c, accurate fluorescence location discrimination would not be possible. In particular, it is necessary to provide reflecting plates 54 for reflecting the fluorescence in gaps between the crystals that structure the scintillator 52 in order to be able to discriminate which of the crystals, arranged in the height direction, indicated by the shading in FIG. 21, was the crystal that emitted the fluorescence.
The structure of the reflecting plates 54 will be explained. There are two sets of reflecting plates 54, those extending in the crosswise direction and those extending in the lengthwise direction, each having the same height as the crystals. The reflecting plates 54 that extend in the crosswise direction and the reflecting plates 54 that extend in the lengthwise direction are fitted together so that the reflecting plates 54 structure a grid-shaped reflecting plate lattice. The crystals are arranged so as to fit into the reflecting plate lattice. FIG. 22 illustrates the reflecting plate lattice schematically.
The scintillator 52 of a conventional radiation detector 51 is structured by stacking, in the height direction, scintillator crystal layers wherein scintillator crystals c are arranged in the lengthwise and crosswise directions by fitting the crystals into reflecting plate lattices. When manufacturing this type of scintillator 52, the number of reflecting plate lattices must equal the number of layers of scintillator crystals. For example, manufacturing the scintillator 52 of FIG. 21, which has four scintillator crystal layers, requires four reflecting plate lattices.
However, in recent years a scintillator 52 of a new structure has been developed. Specifically, it is a scintillator 52 wherein the crystals c in FIG. 21 are monolithic in the height direction, as illustrated in FIG. 23. The use of such a scintillator 52 improves the sensitivity of the radiation detector 51. Unlike the structure that has four layers of scintillator crystals as shown in FIG. 21, with the scintillator 52 of FIG. 23, the fluorescence is able to arrive reliably at the photodetector 53 (see, for example, International Patent Application Publication WO 2009/101730).
Such a scintillator 52, explained using FIG. 23, is also provided with four reflecting plate lattices that are structured from reflecting plates 54. The reflecting plate lattices enable the radiation detector 51 to discriminate the location of the emission of the fluorescence for the vertical direction.
However, the conventional radiation detector has problems. Specifically, the conventional radiation detector 51 is difficult to manufacture.
That is, in order to manufacture the conventional scintillator 52 it is necessary to stack four reflecting plate lattices in the height direction and then to load the scintillator crystals into the openings in the reflecting plate lattices. The reflecting plate lattices are structured from rectangular reflecting plates, and are flexible. Stacking four such flexible reflecting plate lattices is not easy. Consequently, manufacturing a scintillator 52 with the conventional structure requires rather complex operations. If the scintillator 52 is difficult to manufacture, the manufacturing cost of the radiation detector 51 is commensurately higher.
Moreover, with the conventional scintillator 52, four individual reflecting plate lattices must be prepared. When the reflecting plate lattices must be manufactured individually, the number of components for structuring the reflecting plate lattices is increased commensurately, and more labor is required when manufacturing the reflecting plate lattices. This labor further complicates the manufacturing of the scintillator 52, resulting in a commensurate increase in the manufacturing cost of the radiation detector 51.